The video above, filmed by Dr. Olena Kamenyeva from the National Institute of Health, took first place. It shows the immune response in the lymph node of a mouse, when it was activated by a laser—and it's deeply mesmerizing.

The other entries are worth a watch, too. Dr. Stefan Lüpold, from Syracuse University, scooped second place with this video. It shows sperm from two different males (green and red) competing within the reproductive tract of a female fruit fly. Eye-opening.
Third place was taken by Dr. Nils Lindström from the University of Edinburgh with this time-lapse, which reveals how the kidney cells of mice develop over the course of four days.
Finally, our favorite runner-up was filmed by Dr. Oleg D. Lavrentovich from Kent State University. It shows the amazing fluid dynamics of liquid crystals: the changing colors are a result of shifts in the molecular orientation of the flowing liquid. Beautiful.
You can find a round-up of other notable entries over on the Nikon website
. [Nikon
]